Issue with Volume Absorption inside Glass
I was facing the same issue when doing the Blender guru tutorial. I tried searching in a lot of threads for multiple hours but did not find a solution that worked. Then, I found an alternative method from a blender StackExchange thread that worked quite well for me. It talks about tweaking the IOR values of the faces of the coffee which face the glass.  The link for the thread is given below -
Liquid IOR
Image before tweaking the IOR value-

After tweaking the IOR value of the coffee faces by following the solution in the link and setting it to 0.8-

IOR set to 0.91 based on the formulae used in the link-

You can play around with values further to get the desired look.